(Maoming rectangular retort) was built up in December internal-heating cylindrical retort (Maoming cylindrical retort) of 180t/d

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1 415 OIL SHALE RETORTING TECHNOLOGY IN MAOMING Lin Yihe ( #'i&fp ) Petroleum Industrial Corporation, SINOPEC, China ABSTRACT Two batteries of 48 gas combustion rectangular retorts and two batter ies of 64 cylindrical retorts, were established in sixties for processing oil shale with high moisture and low Fischer assay. Rich operation experiences have been accumulated. Study on improvement of retorting technologies is under way. INTRODUCTION The proven oil shale reserves in area give a shale oil equiva lent of several hundred million tons. Petroleum Industrial Corpor ation began research & development of various retorts in mid-fifties. An internal-heating cylindrical retort ( cylindrical retort) of 180t/d throughput and related shale oil processing equipment were built up in March A gas combustion rectangular retort of throughput 96 t/d ( rectangular retort) was built up in December Another gas combustion rectangular retort of throughput 180 t/d ( rectangular retort), and jalousie-type retort were built up in November Testing was made on these retorts in a period of four years. The oil yield (again st Fischer assay) of cylindrical retort, and rectangular retort reached 74%, and 85% respectively. Based on the data from the test re torts, two batteries of 48 gas combustion rectangular retorts of total capacity of 100,000 t/year shale oil and an open pit mine of an equivalent oil shale production were established in early sixties. In late sixties and early seventies two batteries of 64 cylindrical retorts of total cap acity of 100,000 t/year shale oil and oil shale mine were added. This paper gives a description of commercial scale retorting plants and the properties of shale oil produced.

2 416 COMMERCIAL SCALE RETORTING PLANTS IN MAOMING The commercial scale retorting plants discussed include rectangular retort and cylindrical retort. 1. rectangular retort The retort structure is shown in Fig. 1. c: HlOMlnunnli,1 irz^l^ A 7U C C 0 O^f/jCJ P^H? K o/ Jill Fig. 1 rectangular retort structure 1 --Pyrolysis section; 2--gas combustion section; 3-- cooling section. After crushing and screening, oil shale of lump size mm is tran sported by a belt conveyer to the shale bin at the top' of the retort, and then fed into the retort by a charger. Oil shale is redistributed on passing an archway. Drying and retorting of oil shale take place in the pyrolysis section heat transfer between oil shale and hot heat carrier gas from the gas combustion section. Retorted shale char descends to the gas combustion section, where gasification of shale char with preheated gasand air takes place. The heat released in gasification raises the temperature to about 1,000 C. Shale ash is cooled by incoming cold gas in the cool-

3 417 ing section to lower than 300C and then pushed out into the ash trough, where it is further cooled by water to about 70C and discharged by a scraper. An excess of cold gas is introduced into the retort to keep the com bustion temperature in the gas combustion section lower than the fusion point of shale ash, thus in turn preventing sintering of shale char. The condensation and oil recovery system for rectangualr retort is shown in Fig. 2. Fig. 2 The condensation system for rectangular retort 1retort, 2--water seal, 3gathering pipe, 4 scubber pipe, 5 ammonia 6 tower, cooling tower, 7 gas exhauster, 8 air blast blower. The gaseous product from the retort is drawn into the gathering pipe at C, and spray-cooled by recycling dilute ammonia water. The enained dust is removed and large part of shale oil is condensed. The gas temperature is lowered to 72-77C after spray washing. The gas is further cooled by recycling water in scrubber pipes and some more shale oil is recovered. Then ammonia is recovered in ammonia absorber. The gas passes through a cooling tower for condensation of oil vapor and is cooled to about 45C. Then gas passes to an exhauster. Most of the gas is sent back to teh retort as combustion gas and cooling gas. The balance is vent ed to atmosphere through a stack. Separaters and recycling pumps are in stalled in the condensation-recovery units. The throughput of one rectangular retort is t/day (on wet basis of oil shale) with cross sectional intensity of kg/m2hr.

4 418 The retort effluents are in Table 1. Table 1. Retort effluents (rectangular retort) Shale oil kg/ton shale 50 Oil yield against Fischer Assay, % 70 Gas naphtha, 8 Ammonia, 1.5 Hydrogen sulfide, 4.4 Surplus gas, NmVton shale 385 kcal/nm3 605 Heating value of gas, Gas composition C02 % 14.2 h^ ^ 8.6 C H n m % 0.2 CH- 4 % 1.9 N2 % % 0.9 CO % 6.4 Shale oil produced in rectangular retort is a brownish black paste at room temperature, with pungent odor. ic oil, with more paraffin and less asphalt. It belongs to the paraffin The oil properties are list ed in Table 2. Table 2 shale oil properties (rectangular retort) 20 Specific gravity, l>4 Solidification po int, C 32 Kinematic viscosity, centistokes 50< 'C 10.1 Engler distillation Elemental ana lysis IBP C 219 C % % C 273 H % % C 296 S % % C 321 N % % C % % C 362 C/H cylindrical retort cylindrical retort is developed on the basis of Fushun-type retort, with an external mixing chamber in the middle for circumferential gas intake (Fig. 3). Pyrolysis and gasification take place in the same retort. Shale char after pyrolysis goes for gasification, the sensible heat of gasification gas provides for the part of heat required in pyrolysis. The remaining heat comes from the hot recycle gas, which is the gas produced in the re-

5 419 Fig. 3. cylindrical retort structure 1--pyrolysis section; 2mixing section; 3--gasification section. tort inself, heated to 6Q0-650C in a regenerative heater. Hot recycle gas enters the retort from the middle, mixed with the gas from the gasific ation section to exchange heat with down-moving heating oil shale. Drying, pre and pyrolysis of oil shale take place in the pyrolysis section. Pyrolysis comes to completion as shale descends to the central arch at 600 C. Oil vapor from the decomposition of organic matter in oil shale is drawn out from the top of the retort along with the heat carrier gas. As shale char moves downward into the gasification section, the reaction tem perature can be as high as 1,000C. The air blast is humidified to control this temperature below the fusion point of shale ash. Humidification is achieved through passing air blast in a saturator in contact with hot water and additional steam, supply. The moisture content of oil shale amounts to 12-24%, averaging 17% (wet basis). The moisture evaporated increases the amount of gaseous product, the heat carrier gas is also increased accordingly. An external mixing chamber is designed to lower pressure drop due to excessively high

6 420 flow resistance. Disintegration of oil shale during retorting causes smaller voids among the shale lumps and in turn higher resistance to gas flow. Channelling through the space between retort wall and shale charge may re sult in uneven distribution of gas flow. Therefor many gas intake holes are provided on the three legs of arch in the middle section of the retort it enables more or less even flow of the heat carrier gas. The condensation and oil recovery system for cylindrical re tort is shown in Fig. 4. r\ Ka i s I s V m -d Fig. 4. The condensation system for cylindrical retort 1--recuperative heater, 2--retort, 3--water seal, 4--gathering pipe, 5--srubber, 6--ammonium sulfate tower, 7--precooler, 8--saturator, 9--final cooler, 10--gas exhauster, 11,12 air blast blower. The gaseous product is drawn from the retort at about 100C into the gathering pipe, where it is spray-washed and cooled to 73-76C by recycl ing dilute ammonia water to remove dust and condense part of the shale oil Some ammonia water, shale oil and shale dust turn into oil sludge and is separated in the sedimentation tank. The gas is further cooled by recycling water in scrubber and some more shale oil is recovered. It then passes through a precooler, which is in stalled coaxially above the air saturator. Recycling cooling water of 66 C is used tc cool the gas to 71-72C. Cooling water at 72-73C overflows

7 421 through the. water seal between the two towers into the air saturator, where air blast is heated and humidified to a dew point of 66-68C. The recycling water temperature from the saturator drops to 66C. Shale oil condensed is separated in the saturator tank. The gas after precooler is sent into the ammonia absorber, where sul furic acid solution is used to absorb ammonia. The gas after ammonia recovery passes through a final cooler, where it is spray washed by 35-40C cooling water and cooled to 45-50C. Part of shale oil is recovered in the final cooler. An exhauster is installed after the final cooler. About 77% of the gas is heated in a regenerative heater and serves as heat carrier for retorting, the remaining gas is used as heater and boiler fuel. A natural draft cooling tower is used in cir culating cooling water. The operation parameters in recent year are listed in Table 3, the re tort effluents in Table 4. Table 3. Operation parameters of cylindrical retort Throughput, t/day, retort (wet basis) kg/m2 Cross section intensity, hr 638 Shale size, mm Shale moisture, % (wet basis) Fischer assay, % (wet basis) Oil yield vs. Fischer assay (not including gas naphtha), % Air flow rate, Nm3/ton shale 132 Recycle gas, Nm3/ton shale 953 Recycle gas temperature, C 586 Air blast saturation temperature (dew point), C 65 Retort exit gas temperature, C Table 4. Retort effluents from cylindrical retort Shale oil, kg/ton shale Gas naphtha, Ammonia, Hydrogen sulfide, Surplus gas, Nm3/ton shale Heating value of gas, Gas composition kcal/nm CO % 3.7 C(L % 18.3 % % 18.2 CH* % 1.5 r. % 7.3 >n m / o: 0.4 N % 50.4

8 422 As compared with the shale oil produced in rectangular retort, the shale oil from cylindrical retort has a smaller specific gravity and lower solidification point, its properties are listed in Table 5. Table 5. shale oil properties (cylindrical retort) 20 Specific gravity Dt Solidification point, C 30 Kinematic viscosity, centi stokes 50C 9.6 Paraffin content, % 13.2 Asphalt content, % 1.54 Gum (sulfuric acid), % 43 Carbon residue % 2.2 Tar acid, % (vol) 2.8 Engler distillation Elemental analysis IBP C 214 C % % C 259 H % % C 283 S % % C 306 N % % C % % C 350 C/H 7.40 Rich operation experiences have been accumulated in the research and development of oil shale retorting technology in for the 30 years since However, there are some weak points in cross section inten sity and oil yield as compared with the world state-of-the-art technology. A study for upgrading retorting technology is now under way in a newlybuilt testing cylindrical retort. 1. Addition of pre-drying facility. Oil shale charge is to be dried before entering the retort. 2. New retorting technology The gas after final cooler will all be used for recycling to supply the retorting demand to the greatest possible extent. The burning loss of shale oil produced will be minimized. 3. Improvement of condensation-recovery system From the analysis of shale ash from the cylindrical retort, almost no oil can be found in shale ash. The shale oil loss can^be ascribed to gas inclusion, emulsified oil and oil sludge, in addition to burning in the retort. raising Improvement of concensat ion-recovery oil yield. system will contribute to

9 423 CONCLUSION The rectangular and cylindrical retorts are characterized by simple structure, capability of processing oil shale with high moisture (20%); low Fischer assay (4-6%), and low organic carbon (4-8%) in shale char while maintaining heat self-sufficiency. These two types of retorts have been operated for more than 20 years. a long period. The burning remains to be solved. They are easy to operate in of shale oil in the gasification section

W. D. WANG *, C. Y. ZHOU

W. D. WANG *, C. Y. ZHOU Oil Shale, 2009, Vol. 26, No. 2, pp. 108 113 ISSN 0208-189X doi: 10.3176/oil.2009.2.03 2009 Estonian Academy Publishers RETORTING OF PULVERIZED OIL SHALE IN FLUIDIZED-BED PILOT PLANT W. D. WANG *, C. Y.